Vacuum-insulated steam-injection system for oil wells



Aug. 20, 1968 c. w. OWENS ET AL 3,397,745

VACUUM-INSULATED STEAM-INJECTION SYSTEM FOR OIL WELLS Filed March 8, 1966 FIG. 1,

M h INVENTORS CARL W OWE/v.5, /6 1" 64 B NJAM/N 0. OWE/v5 B) THE/R ATTORNEYS HARE/5, M50 Passe/.4 8: AER/v United States Patent 3,397,745 VACUUM-INSULATED STEAM-INJECTION SYSTEM FOR OIL WELLS Carl W. Owens and Benjamin D. Owens, Long Beach,

Calif., assignors, by direct and mesne assignments, of thirty percent each to Carl Owens, M. Dudley Hughes, and Viw'ane Caskey; five percent each to James J. Baker and Jack Owens, all of Long Beach, Calif.

Filed Mar. 8, 1966, Ser. No. 532,780 6 Claims. (Cl. 166-57) ABSTRACT OF THE DISCLOSURE In an apparatus for delivering a heated fluid to a subterranean productive formation having a well drilled thereinto, the combination of an inner, injection tubing in the well and communicating at its lower end with the productive formation, an outer, insulating tubing surrounding said injection tubing and having an inside diameter greater than the outside diameter of said injection tubing to provide a space between said insulating and injection tubings, means closing the upper and lower ends of said space, means connected to the upper end of said injection tubing for introducing a heated fluid thereinto, means connected to the upper end of said space for at least partially evacuating same, said means closing the lower end of said space including packer means carried by the lower portion of one of said tubes and Slidably engaging and sealing with the other of said tubes to accommodate relative longitudinal expansion and contraction of said tubings, and means maintaining the tubings in radial spaced relationship.

The present invention relates in general to increasing the production of Wells drilled into subterranean formations containing materials the fiuidities of which can be increased by the application of heat thereto. More particularly, the invention relates to injecting heated fluids into the subterranean productive formations to increase the fluidities of the materials therein which are to be produced.

The invention is particularly applicable to increasing the production of oil wells drilled into subterranean productive formations containing heavy, i.e., viscous, crudes. By injecting steam at high temperatures and pressures into heavy crude formations, the viscosities of the crude oils therein frequently can be reduced sufficiently to increase production materially. Consequently, the invention will be considered in such an environment herein for convenience.

Stimulation of crude oil production by steam injection is currently carried out in two different ways. In accordance with one practice, steam at high temperature and high pressure is injected into the productive formation continuously from a central injection well. Concurrently, the formation is produced from production wells spaced outwardly from the injection well. The high temperature and high pressure steam introduced into the formation through the injection well in accordance with this practice not only heats the oil in the formation to reduce its viscosity, but also drives it outwardly away from the injection well and toward the production wells.

In accordance with another current practice, commonly referred to as push-pull steam injection, high pressure and high temperature steam is injected into the formation from a well drilled thereinto for a matter of days or even weeks. After the desired quantity of steam has been injected, the well may be permitted to soak for ice several days to provide time for the heat from the injected steam to penetrate the formation substantial distances, and thus reduce the viscosity of the oil therein. Subsequently, the well is produced, usually by pumping, and achieves materially increased production rates as the result of the reduction in the viscosity of the oil achieved by the heat from the injected steam. Frequently, materially higher production rates are maintained for several months or more. Ultimately, when production falls off excessively, this push-pull injection technique can be repeated.

The present invention may be utilized to inject steam into an oil producing formation in accordance with either of the injection and production techniques hereinbefore discussed.

When steam is injected into an oil producing formation in accordance with practices currently in use, the steam flowing downwardly through an injection tubing in the well loses a tremendous amount of heat, primarily through radiation from the injection tubing, before it ever reaches the level of the subterranean productive formation into which it is to be injected. A typical heat loss is 200,000 B.t.u. per hour per foot of injection tubing. Since the injection tubing may be several thousand feet long, it will be apparent that the hourly heat loss can amount to many million B.t.u.

Not only is the foregoing heat loss highly undesirable from the economic point of view, but it can also result in serious damage to the well. For example, in most wells, various fluid-bearing formations are cemented off to prevent entry into the well of undesirable fluids, such as water. The cement utilized to seal otf such formations ultimately deteriorates, from the effects of heat radiated by conventional steam injection tubings, to such an extent that it is no longer effective, thereby permitting the entry into the well of undesired fluids.

With the foregoing as background, the primary object of the present invention is to minimize heat losses from the injection tubing, thereby resulting in substantial economic savings and minimizing well damage.

More particularly, an important object of the invention is to minimize heat losses from the injection tubing by maintaining at least a partial vacuum around the injection tubing, preferably throughout substantially its entire length.

Still more particularly, an important object of the invention is to provide an injection system wherein an outer, insulating tubing surrounds the injection tubing, preferably throughout substantially the entire length of the injection tubing, and wherein at least a partial vacuum is maintained in the space between the injection and insulating tubings to provide a heat insulating barrier mini- 'mizing heat losses from the injection tubing. With this construction, the heat losses from the injection tubing can be held to but a small percentage of the heat losses from an uninsulated injection tubing, which is an important feature of the invention.

Considering the present invention more specifically now, important objects thereof are to provide an injection system which includes: an inner, injection tubing in the well and communicating at its lower end with the productive formation; and outer, insulating tubing surrounding the injection tubing and having an inside diameter greater than the outside diameter of the injection tubing to provide a space between the insulating and injection tubings; means closing the upper and lower ends of such space; means connected to the upper end of the injection tubing for introducing steam, or other heated fluid, thereinto; and means connected to the upper end of the space between the two tubings for at least partially evacuating such space. Preferably, the injection system includes means for substantially centering the injection tubing within the insulating tubing in radial directions so as to make the space between the insualting and injection tubings substantially an annular space or annulus.

An important object of the invention is to provide an injection system for the foregoing nature wherein at least one of the tubings is provided with a reflective coating to further minimize heat losses from the injection tubing. A related object is to provide the outer surface of the injection tubing with such a reflective coating.

Another important object is to provide packer means, for closing the lower end of the annulus between the injection and insulating tubings, which is carried by the insulating tubing and relative to which the injection tubing is axially slida-ble to accommodate axial expansion and contraction of the injection tubing. In this connection, it might be pointed out that the injection tubing may lengthen many feet as its temperature increases upon the introduction of high temperature steam into the upper end thereof, such axial expansion being accommodated by the packer means mentioned.

Another object is to provide means for confining the steam discharged from the lower end of the injection tubing to the zone of the well opposite the productive formation to be injected. Related objects are to provide a confining means which includes a packer carried by the lower end of the insulating tubing and engaging the wall of the well, or includes means for introducing a fluid under pressure between the insulating tubing and the wall of the well.

Another object of the invention is to provide removable closure means for temporarily closing the lower end of the insulating tubing until such time as the lower end of the injection tubing is inserted through the packer means for closing the lower end of the annulus between the insulating and injection tubings. With this construction, entry of well fluid into the interior of the insulating tubing is prevented, which is desirable since such well fluid might interfere with developing at least a partial vacuum in the annulus between the two tubings, damage the reflective external coating on the injection tubing, and the like.

Another object is to at least partially fill the interior of the injection tubing with water, or other suitable liquid, after running it through the packer means for closing the lower end of the annulus between the injection and insulating tubings, and before removal of the temporary closure means at the lower end of the insulating tubing, so as to prevent a pressure surge within the injection tubing upon removal of the temporary closure means at the lower end of the insualting tubing.

The foregoing objects, advantages, features and results of the present invention, together with various other objects, advantages, features and results thereof which will be evident to those skilled in the well injection art in the light of this disclosure, may be achieved with the exemplary embodiments described in detail hereinafter and illustrated in the accompanying drawing, in which:

FIG. 1 is a vertical sectional view of an oil well having installed therein a steam-injection system embodying the invention;

FIG. 2 is an enlarged, horizontal sectional view of the steam-injection system of the invention which is taken as indicated by the arrowed line 2-2 of FIG. 1; and

FIGS. 3 and 4 are enlarged, fragmentary, vertical sectional views showing alternative removable closures for temporarily closing the lower end of an insulating tubing forming part of the injection system of the invention.

Referring to FIG. 1 of the drawing, illustrated therein is a well or well bore drilled from the surface 12 (which may be a submerged surface) downwardly into an oil producing formation 14. In the particular installation illustrated, the well 10 is shown as provided with 4 a casing 16 having performations 18 opposite the productive formation 14.

Surmounting and connected to the upper end of the casing 16 is casing head 20 which provides a tapered seat 22. Engaging the tapered seat 22 is a tapered collar 24 from which is suspended an insulating tubing 26 terminating adjacent the top of the productive formation 14.

Surmounting the casing head 20 is a tubing head 28 provided with a tapered seat 30. Engaging the tapered seat 30 is a tapered collar 32 from which is suspended an injection tubing 34 disposed within the insulating tubing 26. When the injecting system of the invention is in operation, the injection tubing 34 preferably projects below the lower end of the insulating tubing 26 into the productive formation 14.

As is conventional in oil well tubings, the insulating and injection tubings 26 and 34 are made up of tubing sections suitably interconnected in end-to-end relation, as by means of couplings, not shown. It will be understood that the insulating and injection tubings 26 and 34 may be thosuands of feet in length.

The insulating tubing 26 is preferably substantially coextensive, lengthwise, with the injection tubing 34. In other words, the insulating tubing 26 extends substantially from the upper end of the injection tubing substantially to the lower end thereof.

The injection tubing 34 is preferably radially centered within the insulating tubing 26 by means of suitable centering devices, one of which is designated in FIG. 1 by the numeral 36, spaced apart vertically along the length of the injection tubing. These are conventional centering devices carried by the injection tubing 34 and engaging the insulating tubing 26. Their function is to maintain an annular space or annulus 40 between the insulating and injection tubings 26 and 34 to minimize heat conduction from the injection tubing to the insulating tubing. To provide an indication of the radial dimensions of the annulus 40, the insulating tubing 26 may be three-inch tubing and the injection tubing 34 may be two-inch tubing. However, other tubing sizes may 'be used.

When the injection system of the invention is in operation, steam at high temperature and high pressure from any suitable source is introduced into the upper end of the injection tubing 34 through a suitable fitting 42. The steam flows downwardly through the injection tubing 34 and is discharged from the lower end of the injection tubing into the well 10 adjacent the productive formation 14. As hereinbefore discussed, the steam penetrates the productive formation 14 to heat the oil therein, thereby rendering the oil less viscous.

In order to minimize radially outward heat losses from the injection tubing 34 intermediate its upper and lower ends, at least a partial vacuum is maintained in the annulus 40 between the insulating and injection tubings 26 and 34. Considering how this is accomplished, the upper end of the annulus 40 is closed by seating of the tapered collars 24 and 32 on the respective tapered seats 22 and 30. The lower end of the annulus 40 is closed by a packer means or packer 44 through which the injection tubing 34 extends. The upper end of the annulus 40 is connected to a suitable source of vacuum, not shown, as by means of a vaccum line 46 connected to the tubing head 28 in communication with the upper end of the annulus 40. For example, the vacuum line 46 may lead to a suitable vacuum pump, not shown. Preferably, the vacuum source is operated continuously to compensate for any leaks in the system.

Preferably, a vacuum of the order of 25 inches of mercury, or more, is maintained in the annulus 40, although this may be varied without departing from the spirit of the invention. With a vacuum in the annulus 40 of this order of magnitude, heat losses :by radiation and conduction from the injection tubing 34 are greatly reduced, which is an important feature of the invention.

To further reduce heat losses from the injection tubing, the injection system is provided with one or more highly reflective coatings for reflecting radiated heat back into the injection tubing 34. While more than one reflective coating may be used, and while such coatings may be applied to various of the surfaces of the insulating and injection tubings 26 and 34, it is preferable, as a practical matter, to utilize a single reflective coating 48 on the external surface of the injection tubing 34. The reflective coating 48 may be made of such materials as aluminum (foil or anodized), chromium, silver, or gold. In many instances, the coating material may be plated on the external surface of the injection tubing.

The combined actions of the partial vacuum in the annulus 40 and the reflective coating 48 on the injection tubing 34 greatly reduce heat losses from the insulating tubing 26. For example, heat loss reductions of in excess of 90% may be achieved with the invention, thereby providing substantial economic savings and minimizing possible damage to the well, which are important features.

Because of the high steam temperatures used in oil-well steam injection, the injection tubing 34 may expand many feet in length upon the introduction of steam thereinto. To allow for such axial expansion, the injection tubing 34 has a sliding fit with the packer 44. To minimize wear as the injection tubing 34 slides relative to the packer 44 in expanding and contracting, the injection tubing preferably includes a lower section 50 havinga polished external surface. The length of Such lower section is sufiicient to accommodate the entire range of axial expansion and contraction of the injection tubing 34.

The invention provides means for confining the injected steam in a zone of the well opposite the productive formation 14. Such confining means may include a conventional packer 52 carried by the insulating tubing 26 adjacent the lower end thereof and engaging the wall of the well 10, i.e., the casing 16 in the construction illustrated. Alternatively, the upward escape of injected steam into upper zones of the annulus between the insulating tubing 26 and the casing 16 may be prevented by pressurizing such annulus with fluid under pressure through a line 54 connected to the casing head 20 in communication with the upper end of the annulus in question. Preferably, the fluid utilized to pressurize the upper portions of the annulus between the casing 16 and the insulating tubing 26 is an inert gas, such as nitrogen, to prevent possible subterranean combustion.

In running the insulating and injection tubings 26 and 34 into the well 10, it is preferable to run the tubing 26 first, and then run the injection tubing 34. As the injection tubing 34 is run in, the lower section 50 thereof ultimately enters the packer 44, as shown in the drawing.

In accordance with the invention, the lower end of the insulating tubing 26 is temporarily closed until such time as the lower section 50 of the injection tubing 34 engages the packer 44 to close the lower end of the annulus 40. The reason for this is to prevent the entry of any fluids in the well 10 into the interior of the insulating tubing 26 since such fluids might interfere with developing the desired vacuum in the annulus 40, corrode the reflective coating 48, and the like.

Referring to FIG. 3 of the drawing, the lower end of the insulating tubing 26 is shown as having threaded thereon a collar 60 terminating in an inwardly directed annular flange 62. Clamped between the flange 62 and the lower end of the insulating tubing 26 is a disc 64 which may be suitably sealed, not shown, to exclude fluids from the interior of the insulating tubing. The disc 64 is provided with sutncient strength to withstand an external pressure due to a head of fluid in the well 10. However, the strength of the disc 64 is insuflicient to withstand the weight of the injection tubing 34 and any load which may be added to the upper end thereof. Consequently, when the lower end of the lower section 50 of the injection tubing 34 passes through the packer 44 and engages the disc 64, it deforms the disc sufliciently to withdraw the periphery of the disc from between the flange 62 and the lower end of the insulating tubing 26. The deformed disc 64 then drops to the bottom of the well 10, as suggested in FIG. 1 of the drawing.

FIG. 4 of the drawing illustrates a similar structure utilizing a disc 66 of thermoplastic material having sufficient strength at normal temperatures to Withstand any external pressure due to a head of liquid in the well 10. However, after exposure to bottom hole temperatures for a time, the disc 66 softens sufliciently to release itself, assuming the bottom hole temperature are sufficiently high for this purpose. If not, it can be knocked out by means of the injection tubing 34, or the structure of FIG. 3 can be used.

After the injection tubing 34 has been inserted through the packer 44, it is preferably filled with water, or other suitable liquid, at least approximately to the level of any liquid in the wall 10, this being done prior to removing the temporary closure at the lower end of the insulating tubing 26. The purpose of this is to prevent any sudden surge of liquid upwardly in the injection tubing 34 upon removal of the closure at the lower end of the insulating tubing 26, which surge might have undesirable shock effects.

Although exemplary embodiments of the invention have been disclosed herein for purposes of illustration, it will be understood that various changes, modifications and substitutions can be incorporated in such embodiments without departing from the spirit of the invention as defined by the claims which follow.

What is claimed is:

1. In an apparatus for delivering a heated fluid to a subterranean productive formation having a well drilled thereinto, the combination of:

(a) an inner, injection tubing in the Well and communicating at its lower end with the productive formation;

(b) an outer, insulating tubing surrounding said injection tubing and having an inside diameter greater than the outside diameter of said injection tubing to provide a space between said insulating and injection tubings;

(0) means closing the upper and lower ends of said space;

(d) means connected to the upper end of said injection tubing for introducing a heated fluid thereinto;

(e) means connected to the upper end of said space for at least partially evacuating same;

(f) said means closing the lower end of said space including packer means carried by the lower portion of one of said tubes and slidably engaging and sealing with the other of said tubes to accommodate relative longitudinal expansion and contraction of said tubings; and

(g) means maintaining the tubings in radial spaced relationship.

2. An injection system according to claim 1 wherein said means maintaining the tubings in radial spaced relationship includes longitudinally spaced centering devices carried by the injection tubing and slidably engaging the insulating tubing to center said injection tubing within said insilillating tubing and out of heat conducting contact therewlt 3. An injection system as defined in claim 1 wherein said packer means closes the lower end of said annular space.

4. An injection system according to claim 1 wherein said injection tubing is provided with a heat reflective jacket about its exterior.

5. An injection system as defined in claim 1 wherein said well is provided with a casing having perforations where it extends into the productive formation, said insulating tubing having a packer spaced above its lower end to seal between said insulating tubing and the casing above the perforations to prevent the flow of heated fluid up- 'said insulating tubing is adapted to be first arranged in the well and said injection tubing is adapted to be subsequently engaged through the injection tubing, a removable closure means carried by the lower end of said insulating tubing for temporarily closing same preparatory to engagement of the injection tubing therethrough and including a deformable closure disc extending transverse the insulating tubing and adapted to be engaged and displaced by the lower end of the injecting tubing.

References Cited UNITED STATES PATENTS Swan 16657 Larsen 16662 Teichmann et a1. 166-38 X Henderson et al. 16639 Doscher 166 11 Closmann et a1. 166-11 Sparlin 16638 X STEPHEN J. NOVOSAD, Primaly Examiner. 

